Material transport tension control system and apparatus

ABSTRACT

A system for controlling tension in transported material in continuous form involving detection of positional displacement and last sense of movement of a tension roller in continuous contact with the material and generation of tension control signals compensatingly affecting material supply or takeup rate, said control signals being generated only upon occurrence of particular conditions of roller displacement and last sense of movement. The system also includes means for generating said tension control signals in digital steps of time duration controlled by system tension correction performance.

United States Patent Inventor Jack B. Knight Richmond, Va.

App]. No. 889,173

Filed Dec. 30, 1969 Patented Oct. 19, 1971 Assignee Philip MorrisIncorporated New York, N.Y.

MATERIAL TRANSPORT TENSION CONTROL SYSTEM AND APPARATUS 10 Claims, 6Drawing Figs.

U.S. Cl 226/25, 226/195, 226/42, 226/111, 318/7 Int. Cl B65h 23/22 Fieldof Search 226/25, 44,

42, 30, lll;3l8/l95,6,7

[56] References Cited UNITED STATES PATENTS 2,707,254 4/1955 Newman etal. 226/30 X 3,385,493 5/1968 Klein et al..... 226/42 3,404,820 10/l968Marano 226/44 X Primary Examiner-Allen N. Knowles Attorney-Watson,Leavenworth & Kelton PATENIEllum 19 I97! 3, 513,975

. sum 1 or 5 34 I -32 5 L 4.6. SPEED SPEED L2 AC. on/vm cv/wmrm I v vERT R DR/VE/P w I I; POS/T/O/V a TENS/0N SPEED L4 DISPLACEMENT CONT/70LCONTROLLER .SE/VSE 4;; SIG/VAL I DETECTOR GENERATOR SPEED CU/VTROLSIGNAL GE/VERA TOR minimum 19 Ian sum 2 or s v PAIENIEDIICI 19 I97! sumu or 5 PATENTEDncT 19 ISTI SHEET an; 5

MINI

MATERlAL TRANSPORT TENSION CONTROLSYSTEM AND'APPARATUS BACKGROUND OF THEINVENTION This invention relates to material processing :in continuousIn various industrial applications, raw material is transported from afeed station to a work station wherein a characteristic ofthe-materialis modifiedand is furthertransporte'd to a takeup stationwhich feedsmaterial utilization'apparatus. :in

many such applications, it is necessary that the material characteristicbe modified under conditions of constant tension in the material.Typical applications requiring such constant tension material transportare 'the'treatment of yarn in clothweaving in the textile industry, thefinishing of paper in the paper-making industry and the feeding of towto form filter plug rods in the cigarette-making industry. Theimportanceof constant tension transport of raw material is'particularlyseen in the last-mentioned application-In accordance with a'common typeof cigarette filter, a tow comprising a bundle of-several thousandcontinuous filaments is shaped into a continuous rod form, an outersheath is applied, and the rod is ultimately severed into individualfilter sections. The tow is first passed through a processing chamberinwhich the filaments are spread out and a plasticizer applied and thenthrough a collection horn and finally to the sheath applying means. Thesheath may be a paper wrapper or according to one specific form aplastic tube which is formed by extrusion with the tow directed into thehollow interior of the tube concurrently with the casting of the tube.It isimportant that the tow be supplied to the sheath applying meansunder a predetermined tension best suited to result in the desiredcharacteristics including dimensional and functional characteristics.

in material processing systems of the foregoing general type, it iscustomary to employ what is designated as a tension roller or dancer toapply tension to the material and associated dancer position monitoringapparatus for generation of signals controlling material feed and/rtakeup speed to maintain tension within certain limits. The dancerelement is generally in the form of a cylindrical roller interposedbetween the feed means and the takeup means, the transported materialbeing passed about the dancer in such a manner that variations in thetension desired in the material give rise to displacements of the dancerand consequently of the position of the plane of contact between thedancer and the material, and correspondingly the path of the materialbetween the feed and the takeup mechanism. The dancer is freely mountedso as to follow the material, being raised or lowered thereby upontension increase or decrease therein. By suitable counterbalancing thedancer may itself exert no tensile force upon the material.Alternatively the dancer may, by virtue of its unbalancedweight, applytension to the material. It may be readily shown that dancer-producedtension in the material is equal to one-half of the unbalanced dancerweight times the arc sine of the angle between the material and saidperpendicular plane in which the dancer moves. Such dancer-producedtension may be maintained at a given level by maintaining said angleconstant, i.e. by maintaining the dancer in a particular contact planewhich may be described as the plane tangent to the dancer surface withinthe arc of contact by the material strip and perpendicular to thedirection of bodily movement of the dancer. The predetermined desiredcontact plane will hereinafterbe referred to as the datum plane.

In certain known systemsusing relativelyinexpensive alternatingcurrenttransport apparatus it is customary to provide a control systemoperatively responsive only to dancer displacement and hence tensionvariation -to modify the speed of the material takeup means.Arrangements of these control systems as are presently known to existprovide relatively coarse tension control, there being an inherenttendency to provide constant or analog controluin one orthe otherdirection at all times resulting in continuing variation of the contactplane and oscillatory tension in thematerial. Close tension errortolerance is beyond thecapabilities of such systems and in situationswhere close tolerance is essential, such as the above-mentioned tobaccon-application, these known tension control systems are ineffective.

Other control systems are presently. known which provide appropriatetolerance controlbut such :systems are characterized by relativelyhighcostsince they are DC systems throughout incontrastto :thexknowncoarse controlsystems which permit the use of lesszexpensivewvariablespeed AC transport apparatus. 1

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved system for controlling tension in transported material. I

It is a more particular object of this invention to provide a tensioncontrol system operatively responsive to a tension roller to provideclose tolerance tension control with substantially no oscillatorytendency.

It is a further object of this inventiontto provide a tension controlsystem permitting variable speed-AC material transport with closetolerance of material tension.

It is an additional object of this invention to provide a tensioncontrol system wherein noncontinuous or digital tension correction isselectively initiated in response to tension roller movement.

It is a further object of this invention to provide improved tensionroller movement sensors for constant tension control systems.

It is an additional object of this invention to provide an improvedmaterial transport system incorporating separately operative coarsespeed and tension control.

In the efficient attainment of these and other objects there is providedin the present invention first means detecting tension rollerpositionwith respect to said datum-plane and last sense of dancerdisplacement and generating distinct output signals upon occurrence ofpredetermined conditions of tension roller position and last sense ofdisplacement and second means operatively responsive to said-outputsignals to provide tension control signals which increase or. decreasethe speed of operation of material feed means upon. occurrence of saidconditions, thereby maintaining said tension roller in tensileforceapplying contact with said materiab at said datum plane.

Said predetermined conditions for generation of saidoutput signals arethat the tension roller have;departed from said datum plane in a firstor second direction :respectively and not have exhibited a sense ofdisplacementopposite to said first or second direction respectively. Bysuch conditioned. signal generation, the control system of the inventionis effective to initiate tension correction only in instances inwhich notendency toward self-correction has occurred-andto continue tensioncorrection only upon detectinganeed for correction beyond said initialcorrection.

in a particularly preferred. embodiment *of-theinvention, said secondmeans incorporates circuitryfor generating said tension control signalsas a plurality of discrete pulses, each providing incremental speedvariation=-in: said transported material feed means and furthercircuitry. adapted to continually determine the existence ofsaidconditions intermediate generation of each said pulse.

Since system accuracy is dependent to a substantial extent uponfrictionless support of said tensionroller, thereare disclosed in thepresent invention low friction-embodiments of said tension rollerposition and sense oftdisplacement detecting means, one of whichembodies rolamiteelements providing substantially friction-freedisplacementof said tension roller in said perpendicular plane.

The above-and other objectsand features of the invention will.be-evident from the following detaileddescription thereof and from theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagramof a material transport system incorporating the tension control systemof the invention and auxiliary coarse speed controlling apparatus.

FIG. 2 is'a perspective view of a first embodiment of the tension rollerposition and sense of displacement detecting means of FIG. 1.

FIG. 3 is a schematic diagram of preferred circuitry for said detectingmeans and circuitry for use in the tension control signal generator ofFIG. 1.

FIG. 4 is a schematic diagram of preferred circuitry for said tensioncontrol signal generator.

FIG. 5 is a perspective view of a preferred embodiment of the tensionroller position and sense of displacement detecting means of FIG. 1.

FIG. 6 is a side elevation of the apparatus of FIG. 5 as seen from lineVl-Vl.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 raw material 10 istransported to material takeup station 12 from material feed station 16,stations 12 and 16 respectively including takeup rolls 18 and 22normally maintained at constant speed and feed rolls and 24 subject toadjustable fine speed control. The feed rolls draw continuous towmaterial 10 from a suitable supply coil, the material being passedthrough suitable processing means wherein a dimensional or likecharacteristic of the material is altered en route to the feed rolls, ifdesired. Material 10 is transported about guide roller 26, under tensionroller 28 and about guide roller 30. The lower periphery of roller 28 isto be maintained in continuous contact with the material at datum plane32 to exert a predetermined force upon the material and define aparticular tensile force therein. Material 10 will thus be drawn throughsaid processing means under constant tension as long as roller 28contacts material 10 at datum plane 32.

Takeup station 12 comprises an AC driver 34, the output shaft 36 ofwhich is rotated at a constant speed. Speed converter 38 is coupled toshaft 36 and provides variable coupling between same and its outputshaft 40 in accordance with control signals applied from speedcontroller 42 over lines 44 and 46. The composite element grouping 34-46may comprise a conventional variable-speed AC drive transport such asthe Reeves Varidrive produced by the Reliance Electric Co., Cleveland,Ohio. In such arrangement unit.38 incorporates a small AC gear motorwhich is selectively connected to normal phase or reverse phase ACexcitation through speed controller 42 which may comprise a simplebipolar switch. As the motor is excited with normal phase AC excitationmechanical coupling between shafts 36 and 40 is varied such that thespeed of shaft 40 is reduced. Conversely, with speed controller 42operated in the opposite manner to provide reverse phase AC excitation,the rotational speed of shaft 48 is increased.

A complementary arrangement is incorporated in material feed station 16wherein AC driver 48 has'an output shaft 50 coupled to speed converter52, the output shaft 54 of which is speed-controlled in accordance withsignals appearing on lines 56 and 58. In contrast to corresponding lines44 and 46 of station 12, lines 56 and 58 of station 16 are connectedwith normal and reverse phase AC excitation either through lines 60 and62 or lines 64 and 66. As will be presently clear, lines 60 and 62provide such excitation, hereinafter speed control signals, for purposesof insuring equal feed and takeup of material 10. Lines 64 and 66provide such excitation, hereinafter tension control signals, to directunit 52 in modify- 'ing feed speed irrespective of material takeup rate.As will also be presently evident, lines 64 and 66 are integral with thenormally operating tension control system of the invention whereas lines60 and 62 are associated with the normally quiescent speed controllingapparatus employed in the FIG. 1 system.

In the generation of signals on lines 60 and 62, a mechanical interlink68 is provided between speed controller 42 and speed control signalgenerator 70 such that unit 70 is operative to generate output signalsonly upon manual operation of unit 42. Instantaneous indication of therate of takeup of material 10 by feed station 12 and of advance of thematerial by station 16 is provided to unit 70 over lines 72 and 74respectively, same being connected to sped sensors 76 and 78 whichreceive input signals from shafts 80 and 82 respectively connected toshafts 40 and 54. Sensors 76 and 78 are typically tachometer generatorsproviding direct current signals respectively proportional to the speedsof the input shafts thereof.

In operation of the system of FIG. 1, if it is desired at any time toincrease or decrease material transport speed, or to perform a check ofrelative rates of feed and takeup, speed controller 42 is operated bymanual actuation of switching assemblies thereof associated withincreasing, decreasing or monitoring transport material speed. In thecase of an increase or decrease in transport rate, AC excitation isapplied at normal or reverse phase through lines 44 and 46 to variablespeed unit 38 to provide speed variation in shaft 40. A signalindicative thereof is generated on line 72 and speed control signalgenerator 70 responds to said signal and the signal then provided online 74 and indicative of the speed of shaft 54 to apply AC excitationto lines 60 and 62 of phase and time extent to set speed converter 52such that shaft 54 speed is slaved to shaft 40 speed and the signals onlines 72 and 74 are equal. Such coarse speed adjustment is normallyperformed during system startup and at selected other times, the speedcontrol apparatus described being generally inoperative during thenormal course of material transport.

After such initial system setup and with feed rate tracking takeup rate,tension roller 28 is counterbalanced such that datum plane 32 definesthe plane of contact of the roller with the transported material, thetransported material defining the angles 0 with plane 32. Mechanismssupporting roller 28 and providing such counterbalancing will bediscussed in connection with FIGS. 2, 5 and 6. The tension roller isconnected by mechanical linkage 84 with tension roller position anddisplacement sense detector 86. This unit contains a plurality of switchmembers operated by linkage 84 in accordance with both the positionaldisplacement of roller 28 above or below datum plane 32, i.e. departuresfrom the position illustrated in FIG. 1, and the last sense ofdisplacement of the roller, i.e. upwardly or downwardly in FIG. 1. Bysuitable interconnection of said switch elements, predetermined signalgenerating conditions are established in unit 86 and signals aregenerated on lines 88 and 89 upon the occurrence of first conditionsrequiring an increase in feed speed for tension correction and on lines88 and 90 upon the occurrence of second conditions requiring tensioncorrecting reduction in the speed of operation of the feed apparatus.

Lines 88, 89 and 90 are connected to tension control signal generator 92which includes circuitry operatively responsive to signals provided onsaid lines to apply AC excitation to lines 64 and 66 of phase and timeextent sufficient to modify operation of variable speed unit 52 todirect variation in feed speed to initiate return of roller 28 to datumplane 32. Mechanical interlink 93 may be provided between speedcontroller 42 and detector 86 to discontinue excitation of unit 86, andhence interrupt tension control, during operation of the speedcontroller.

Referring to FIG. 2, wherein a first embodiment of tension roller 28,linkage 84 and tension roller position and displacement sense detector86 is illustrated, the tension roller 28 is mounted on a shaft 94 seatedin bearings 96 and 98. Side walls 100 and 102 define vertical tracks 104and 106 having rails 108, 110 and 112, 114 which guide movement ofbearings 96 and 98. Blocks 116 and 118 are secured to shaft 94 andmechanical linkage 84 takes the form of a pair of support cables 120 and122 respectively connected to blocks 116 and 118 at first ends thereofand to pulleys 124 and 126 at the other ends thereof. The pulleys arefixedly mounted on shaft 128 which is seated in bearings 130 and 132fixedly supported by arms 134 and 136. Shaft 128 fixedly supports afurther pulley 138 to which is secured one end of cable 140, the cablebeing connected at the other end thereof to a counterweight 142. Asdiscussed above, counterweight 142is selected in accordance with theunbalanced tension roller force desired to be applied to transportedmaterial to develop a predetermined tensile force in the material duringtransport thereof.

The foregoing apparatus comprises tension roller support and guide meanseffective to impart rotation to shaft 128 in and includes a cam contourhaving first and second continuous concentrically displaced sections148a and 148b respectively engaging cam follower 146 when tension roller28 departs upwardly or downwardly from the position thereof illustratedin FIGS. 1 and 2. Thus switch 144 assumes one state when the tensionroller departs upwardly from datum plane 32 as a result ofcounterclockwise rotation of shaft 128 and assumes its other state whenthe tension roller departs downwardly through datum plane 32 whereuponshaft 128 is rotated in a clockwise direction. Second and third switches150 and 152 are operated by actuating arm 154 which is connected toshaft 128 through a bidirectional slip clutch 156. Switches 150 and 152are closely placed about actuator 154 and by reason of the slip clutchmounting of the actuator the switches, as operated, act as stop members,restricting total angular displacement of actuator 154 to a limitedarcuate path of approximately 6 As shaft 128 is rotated 3counterclockwise, actuator 154 operates switch 151) and the switch willremain operated until clockwise rotation of shaft 128 occurs whereuponthe actuator will operate switch 152 substantially immediately, i.e.upon about 6 of clockwise rotation. The converse situation will now bemaintained, i.e. switch 152 will be maintained in its operated conditionuntil the direction of rotation of shaft 128 again reverses. Evidentlyshaft 128 will be rotated in an initial counterclockwise direction uponany upward movement of tension roller 28 and switch 150 will beoperated. Switch 152 will be operated by any downward movement of thetension roller.

The above-discussed predetermined conditions for generation of signalson lines 88, 89 and 91) of FIG. 1 by operation of switches 144, 150 and152 by the mechanism of FIG. 2 will be evident from the switchinterconnection circuitry of FIG. 3.

Two sources of supply potential are provided for the circuitry of thetension roller position and sense detection means 86 and tension controlsignal generator 92. A direct current potential is provided by supply158 over lines 160 and 162 and alternating current potential is providedby supply 164 over lines 166 and 168. The former supply is provided onlyfor low level signal generation in unit 86 whereas the latter supply isemployed for generation of unit 92 control signals and for powering theAC drive apparatus of feed station 16. Terminal 150-1 of switch 150 isconnected to line 160 and terminal 152-1 of switch 152 is connected toline 162. The switches include contact arms 150-2 and 152-2 operated asdescribed above by actuator 154, movement of the actuator beingclockwise or counterclockwise as illustrated. Switch 144 includes afirst terminal 144-1 connected by line 170 to the remaining terminal150-3 of switch 150 and a second terminal 144-2 connected by line 172 toterminal 152-3 of switch 152. The contact arm 144-3 of switch 144 isconnected to output line 88, contact arm 144-3 being displaced by camfollower 146 in transverse directions as illustrated. Output lines 89and 90 are connected respectively to supply lines 160 and 162.

While lines 89 and 90 are continually provided with positive andnegative potentials respectively, output line 88 will be selectivelyenergized by a positive or negative potential or will be unenergizeddepending'upon the operation of switches 144, 150 and 152 by switchactuators 146 and 154. Referring to both FIGS. 2 and 3 if roller 28assumes a position above datum plane 32, cam follower 146 assumes itsleftward position placing contact arm 144-3 in engagement with terminal144-1. Output line 88 will then receive apositive potential if switch150 is closed or will be unenergized ifswitch 150 is open. Since switch150 will be closed byactuator 154 upon upward movement of roller 28, thecondition by which output line 88 will receive a positive potential isthat the roller have assumed said position above datum plane 32and havenot initiated a return movement to the datum plane. Conversely, ifroller 28 is positioned downwardly with respect to datum plane '32, camfollower 146 assumes its rightward position and contact arm 144-3engages terminal 144-2. Line 88 will receive either a negativepotentialor will be unenergized depending upon the state of switch 152.Switch 152 will be closed with contact arm 152-2 engaging terminal 152-3upon any downward sense of movement of roller 28 and will remain closeduntil upward movement of the roller occurs. Thus, the condition wherebyline 88 will receive a negative potential is that the roller havedeparted downwardly with respect to datum plane 32 and not haveinitiated a return to the datum plane. Line 88 will be unenergizedunder'all conditions other than the described conditions of continuitybetween said line and DC source 158 by said switches. Thus, controlcircuitry depending upon lines 88, 89 and for operation will beoperative only during the occurrence of said conditions and tensioncorrection will occur only when the roller has been displaced from itsdesired position of registry with datum plane 32 and has not exhibited,by self-correction or like occurrence, a tendency to return to saiddatum plane position. By virtue of this system feature, the subjectcontrol system avoids the tendency to perform tension correction duringthe occurrence of self-correction or of system-initiated tensioncorrection and the likelihood of overcorrection, repetitively directingroller 28 through and above and through and below the datum plane, isavoided rendering the system substantially oscillation-free.

A simplified version of tension control signal generator 92 is alsoshown in FIG. 3, comprising a bipolar relay 174. The relay incorporatesa center tapped winding having sections 174-1 and 174-2, the formerbeing connected across lines 88 and 89 and the latter being connectedacross lines 88 and 90. Evidently, when line 88 is interconnected withline 162, i.e. is negative, no potential difference exists between lines88 and 90 and section 174-2 is unenergized. Under this condition, apotential difference does exist between lines 88 and 89 and section174-1 is energized directing relay contact members 174-3 and 174-4upwardly providing continuity between lines 168 and 64, and betweenlines 166 and66. Conversely, if line 88 is interconnected with line 160,i.e. is positive, no potential difference exists between lines 88 and 89and section 174-1 is unenergized. Under such conditions a potentialdifference does exist between lines 88 and 90 and section 174-2 isenergized directing relay contact members 174-3 and v174-4 downwardlyproviding continuity between lines 166 and 64 and between lines 168 and66. Thus, the'phase of AC excitation provided on lines 64 and 66 will bereversed depending upon the polarity of energization of line-88, lines64 and 66 being unenergized where line 88 is unenergized. Whereas relay174 is illustrated as being of the 'center-tapped type, same may becomprised of a single winding without center tap, having a firstterminal connected to line 88 and a second terminal connected throughresistors to both lines 89 and 90. Current flow through such windingrespectively in one or the other sense will provide first or oppositedirectional movement of the solenoid thereof.

In FIG. 4 there is illustrated a preferred embodiment of tension controlsignal generator 92 wherein the-phase oftension control signalsgenerated at lines 64 and-.66 is provided in accordance with thepolarity of energization of line 88, as in the unit 92 illustrated inFIG. 3, but wherein the periodicity of tension control signals is variedwith respect tothe periodicity of energization of line 88. To thisextent,1thearrangement of FIG. 4 includes a bipolar relay 176having-sections 176-1 and 176-2 selectively actuated in response to thepolarity of energization of line 88 and directing relay contact member176-3 to provide continuity respectively between lines 178 and 180 orbetween lines 182 and 184. Lines 178 and 182 are connected to line 166of supply 164 as designated by the letter A. The letters A and B areemployed throughout the circuitry of FIG. 4 to indicate respectiveconnection of lines to either supply line 166 or 168. Relay 186 isconnected to line 180 for energization and includes a contact member186-1 adapted to provide continuity between lines 188 and 190.Similarly, relay 192 is connected to line 184 and includes a contactmember 192-1 adapted to provide continuity between lines 194 and 196.Lines 190 and 196 are connected respectively to lines 198 and 200through the normally closed contacts 202-1 and 202-2 of time delay ondeenergization relay 202. Time delay on deenergization relay 204 isconnected to line 198 and includes contact member 204-1, adapted toprovide continuity between lines 206 and 208, and 204-2, 204-3, adaptedto provide continuity between lines 166 and 64 and 168 and 66respectively. Time delay on deenergization relay 210 is connected toline 200 and includes contact members 210-l adapted to providecontinuity between lines 212 and 214, and 210-2, 210-3 adapted toprovide continuity between lines 166 and 66 and lines 168 and 64respectively. Lines 206 and 212 are connected to line 166 and lines 208and 214 are connected to line 216, the latter being connected to relay202 for energization thereof.

In describing the operation of the circuit of FIG. 4, it will be assumedthat line 88 has been energized with a negative potential, in turnenergizing section 176-1 of relay 176 whereupon the upper relay contactsare closed by contact member 176-3 and relay 186 is energized throughlines 166, I78 and 180. As the contacts of relay 186 are closed bycontact member 186-1, relay 204 receives energizing voltage throughlines 166, 188, 190, 198 and the normally closed contacts of relay 202.Upon energization of relay 204 lines 166 and 64 are connected throughcontact member 204-2 and lines 168 and 66 are connected through contactmember 204-3 and a tension control signal of first phase is therebygenerated. This control signal will persist on lines 64 and 66 until thetime period for deenergization of relay 204 expires, irrespective ofchanges in state of relays 186 and 202 during such period. Concurrentlywith the generation of the tension control signal on lines 64 and 66,voltage energizing relay 202 is developed on line 216 by closure ofcontact member 204-1 and interconnection of lines 206 and 208. Uponenergization relay 202 will remain energized until the time period fordeenergization thereof expires, continuity between lines 190 and 198being interrupted during such period by displacement of contact member202-2 from its illustrated normally closed position. Since theenergizing path for relay 204 is thereby interrupted, the relay will notbe reenergized upon expiration of the time period thereof and the signalgenerated on lines 64 and 66 will terminate. Assuming relay 186 to becontinued in its energized state at this time, the tension correctionrequirement signal being maintained on line 88 by virtue of thecontinuing need for correction as sensed by detector 86 (FIGS. 1 and 3),lines 188 and 190 of the energizing circuit of relay 204 will remain incontinuity through contact member 186-1. Upon expiration of the timeperiod of relay 202, contact member 202-2 will return to its normallyclosed position and energizing voltage will again be applied to relay204 initiating the cycle of operation heretofore discussed andgenerating on lines 64 and 66 a second tension correction signal of thesame phase. By appropriate selection of the respective time delays ofrelays 204 and 202, a plurality of pulses of desired duration andperiodicity may be provided during the occurrence of the continuoustension correction requirement signal on line 88. Thus, in addition tothe system feature providing for initiation of tension correction onlyupon the existence of the two above-discussed conditions implemented incircuit 86, the system is adapted, by virtue of the circuitry of FIG. 4,to generate noncontinuous or digital error correction signals therebyproviding discrete conditioned correction having even less tendencytoward oscillation than by use of circuit 92 of FIG. 3.

While the circuit of FIG. 4 has been discussed in connection with afirst polarity signal appearing on line 88, it will be evident by virtueof the complementary symmetry in the control circuitry that actuation ofrelay 184, upon the generation of a reverse polarity signal on line 88,will given rise to like operation of relays 202 and 210, relay 210providing for a reverse interconnection of lines 166, 168, 64 and 66through contact members 210-2 and 210-3, thus generating tension controlsignals of opposite phase to those in the above discussed example. Itwill be further evident that the circuitry of FIG. 4 is adapted togenerate continuing discrete pulses on lines 64 and 66 only uponcontinuing conditions for tension correction indicated by maintenance ofsignals of either polarity on line 88. Thus, where the system reactspromptly in initiating error correction, such conditions will notpersist and a single and not a plurality of pulses may be generated.

In the arrangement illustrated in FIG. 2 for support of roller 28,various elements are in frictional engagement somewhat detractive ofsystem performance. While such arrangement is useful in mostapplications, where a particularly high degree of system performance isdesired, the arrangement of FIG. 5 is preferably employed. Thereinroller 28 is supported by a pair of rolamite assemblies 218 and 220. Athird rolamite 222 is included for tension roller sense of displacementdetection. Rolamite assembly 218 has associated therewith a proximityswitch 224 for detecting tension roller position relative to datum plane32. Rolamite assembly 218 is shown in perspective section to illustratethe internal makeup thereof, it being understood that all rolamiteassemblies 218, 220 and 222 are commonly structured. Roller 28 isrotatively supported on shaft 226, one end of which is supported byrolamite assembly 220 and the other end of which is supported by roller228 of rolamite assembly 218. Disposed in nonslipping contact with aportion of the periphery of roller 228 is rolamite band 230 fixed at thelower end thereof to wall 232. Band 230 is further in nonslippingcontact with a portion of the periphery of roller 234 and is affixed towall 236 at the other end thereof. In accordance with rolamitekinematics, rollers 228 and 234 are selected to have diameters differingto an extent providing differential bending moments in band 230 yieldinga net upward force on roller 228 equal to the weight of rollers 228 and234 plus one-half of the weight of roller 28 and shaft 226 minus thedesired force which roller 28 is to apply to transported material.Rolamite 220 is provided with a band of identical characteristics toband 230 and the rollers thereof corresponding to rollers 228 and 234have identical corresponding diameters and weights. A full explanationof the kinematics and performance characteristics of rolamites per semay be found in US. Pat. Nos. 3,452,175 and 3,452,309 and referencethereto is hereby made. Since the rolamite is a substantiallyfrictionfree support bearing, the various frictional constraints onsystem performance, eg slip clutch 156, etc., present in the arrangementof FIG. 2 are avoided.

In order to derive positional information relating roller 28 position todatum plane 32 proximity sensor 224 incorporates a frictionless switchmember actuated when metallic band 230 is within the switch field ofview, i.e. when the band is positioned against wall 232 adjacent sensor224. The switch member is unactuated when band 230 departs from wall232, i.e. when roller 28 is displaced upwardly from datum plane 32. Itwill be evident that this switch performs an identical function toswitch 144 of FIG. 2 in that it assumes alternate states depending uponthe position of roller 28 with respect to the desired plane of contactbetween same and transported material.

In FIG. 6 sensor 224 is mounted in aperture 238 of wall 232, band 230being shown in the sensor field of view. In such position roller 28 isin proper registry with datum plane 32, upward movement from suchposition withdrawing band 230 from the sensor field of view causingsensor 224 to indicate that roller 28 is disposed in a position abovethe datum plane.

Upward or downward last sense of movement of roller 28 is provided bysignals generated in rolamite 222, same being connected by arm 240 torolamite 218. Rolamite 222 incorporates a band 242 and rollers 244 and246 having shafts 248 and 250 interconnected by member 252. As in thecase of rolamite 218, band 242 is fixed to wall 254 at one end and towall 256 at its other end. Arm 240 is bifurcated at one end thereof,arms 258 and 260 receiving shaft 262 of roller 228. Arm 240 is pivotallyconnected to member 252 by pin 264 and collar 266. The arm supports aswitch member 268 which is tilt-sensitive, operated in a first state byclockwise rotation of arm 240 about pin 264 and in alternate state uponcounterclockwise rotation of the arm about the pin. Such rotativemovement of arm 240 is restricted in said two directions respectively bystop members 272 and 274 affixed to connecting member 252. Acounterweight element 270 is variably seated in arm 240 for balancingthe arm. The diameter differential of rollers 244 and 246 of rolamite222 is selected such that the rolling cluster generates an upwardlydirected force equal to the weight of the rollers 244 and 246 and thevarious elements connected thereto. With such diameter selection andcounterbalancing of arm 240, it will be evident that in the neutralposition illustrated rolamites 218 and 222 do not load one another.

Upon displacement of roller 28 upwardly or downwardly from said desiredposition of registry with datum plane 32, arm 240 will be freely pivotedabout pin 264 over a defined are as established by the position of stopelements 272 and 274. Such are is preferably plus and minus threedegrees from the neutral position and the tilt-sensitivity of switch 268is similarly 3 Upon engagement of arm 240 with either of stop members272 and 274, Le. upon vertical travel of roller 28 in a substantialupward or downward direction, rolamite 222 will move in accordance withthe movement of rolamite 218. Such movement will however be essentiallynonloading as respects rolamite 218, rolamite 222 being self-supportingas discussed above.

It will be seen that switch 268 functions in identical manner asswitches 150 and 152 of FIG. 2 constantly providing an indication of thelast sense of displacement of roller 28. By interconnection of sensor224 and switch 268, the aforementioned predetermined conditions forgeneration of tension correction control signals may be readily providedin accordance with the interconnection circuitry of FIG. 3.

While tension roller 28 has been illustrated to have vertical travel inresponse to tension variation in transported material 10, it will bereadily evident that the apparatus of FIGS. 5 and 6 and the apparatus ofFIG. 2 are equally adapted for use in providing the tension roller withhorizontal travel. Furthermore, while the control circuitry has beenillustrated as employing electromechanical elements, same mayincorporate electronic devices in place of same, low power switchingtransistors being useful in circuit 86 of FIG. 3 and high powerswitching transistors or controlled rectifiers being useful in circuit92 of FIG. 3 and the circuitry shown in FIG. 4.

While the control system herein has been illustrated in an applicationwherein tension control is required between first feed and first takeupapparatus, it will be evident that the system may be readily applied incascade to multiple successive pairs of feed and takeup apparatus. Insuch application, the terminal or initial apparatus of each successivepair acts as a master respectively to the initial or terminal apparatusof the next successive pair as does apparatus 12 of FIG. 1 to apparatus16 thereof.

In this connection, various changes and modifications as will be evidentto those skilled in the art may be made in the preferred embodimentsdiscussed in detail above without departing from the spirit and scope ofthe invention, such embodiments being intended in an illustrative andnot in a limiting sense.

What is claimed is:

I. A system for maintaining a particular tension in material incontinuous form transported between material feed mechanism and takeupmaterial mechanism comprising:

a. force-applying means supported for movement in continuous contactingengagement with said transported material and producing said particulartension in said material upon contacting engagement therewith in apredetermined datum plane;

b. means detecting the position with respect to said datum plane and thelast sense of movement of said force-applying means and generatingoutput signals exclusively upon the occurrence of predetermined detectedpositions with respect to said datum plane and predetennined detectedsenses of movement of said force-applying means;

c. a tension controller operatively responsive to said output signals tovary the speed of operation of one of said mechanisms relative to theother said mechanism exclusively during occurrence of said outputsignals to maintain said force-applying means and said material incontacting engagement at said datum plane.

2. The system claimed in claim 1 in which said tension controller isconnected to vary the speed of operation of said material feedmechanism, said takeup mechanism being maintained at a substantiallyconstant speed.

3. The system claimed in claim 1 wherein said force-applying meanscomprises a shaft, a tension roller supported for rotation on said shaftand contactingly engaging said material, said shaft being supported byfirst and second rolamite assemblies for movement relative to said datumplane in accordance with movement of said material, said shaft beingconnected to first rollers of said assemblies.

4. The system claimed in claim 3 including further a third rolamiteassembly having a member interconnecting a first roller thereof to saidfirst roller of said first rolamite assembly, said means detecting thepositions with respect to said datum plane and senses of movement ofsaid tension roller including a first switch member actuated by saidfirst rolamite assembly to one or another state by positioning of saidtension roller on one or the other side of said datum plane and a secondswitch member actuated by said interconnecting member to on or anotherstate in accordance with the last sense of movement of said tensionroller.

5. The system claimed in claim 4 wherein said means detecting thepositions and senses of movement of said tension roller further includescircuitry interconnecting a power supply and said first and secondswitches for generation of said output signals, first output signalsbeing provided exclusively when both said first and second switches areactuated to said one state or when both said first and second switchesare actuated to said other state.

6. The system claimed in claim 5 wherein said first switch comprises aproximity switch actuated by presence of the band of said rolamitewithin the switch field of view, and said second switch is anattitude-sensitive switch affixed to said interconnecting member.

7. The system claimed in claim 1 including a subsystem conforming thespeed of operation of said feed mechanism to the speed of operation ofsaid takeup mechanism comprising:

a. a first signal generator providing an output signal indicative of thespeed of operation of said feed mechanism;

b. a second signal generator providing an output signal indicative ofthe speed of operation of said takeup mechanism; and

c. a speed controller operative alternatively to said tension controllerupon demand to vary the speed of operation of said feed mechanism, andresponsive to differences between said output signals of said first andsecond signal generators.

8. The system claimed inclaim 1 wherein said position and sensedetecting means provides a first or second output signal respectivelyupon the detection of first position with respect to said datum planeand first directional last sense of movement or second position withrespect to said datum plane and second directional last sense ofmovement of said force-applying means, said tension controllerincreasing or decreasing the speed of operation of said feed mechanismrespectively in response to said first or second output signals.

9. The system claimed in claim 8 wherein said tension controllerincludes means operatively responsive to said first or second outputsignal to respectively generate first or second successions of digitalsignals during occurrence of said output signals, each signal in saidfirst or second succession of signals respectively providing incrementalincrease or decrease in the speed of operation of said feed mechanism.

10. The systemclaimed in claim 1 wherein said position and sense ofdetecting means comprises a first shaft, means supporting said firstshaft for translation in a first plane, said shaft supporting a tensionroller in contacting engagement with said transported material, a secondrotatably supported shaft connected to said first shaft and operatedthereby in one or the other rotational direction upon translation ofsaid first shaft respectively in one or the other translationaldirection, a cam affixed to said second shaft for rotation therewith andhaving first and second cam surfaces respectively indicative of theposition of said first shaft above or below a plane transverse to saidplane of translation of said first shaft, cam follower meanscontinuously contacting said cam, a signal generator connected to saidcam follower and providing first or second output signals in accordancewith said positions of said first shaft, a bidirectional slip clutchdriven by said second shaft, an actuator connected to said slip clutchand second and third signal generators disposed on alternate sides ofsaid actuator and respectively operated by said actuator upon clockwiseor counterclockwise rotation of said second shaft and providing outputsignals respectively indicative of first or second senses of translationof said first shaft.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,613,975 Dated October 19, 1971 Invent0r(s) Jack B. Knight It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In Sheets 1 through 5 of the drawings, "3,513,975" should read--3,6l3,975--.

Column 4, line 5, "sped" should read --speed-.

Column 10, line 37, "on" should read --0ne.

Signed and sealed this 1st day of August 1972.

(SEAL) Attest:

EDWARD M.FL5TCHER ,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents )RM PO-1fi50 110-69! uscoMM-nc 603704 69

1. A system for maintaining a particular tension in material incontinuous form transported between material feed mechanism and takeupmaterial mechanism comprising: a. force-applying means supported formovement in continuous contacting engagement with said transportedmaterial and producing said particular tension in said material uponcontacting engagement therewith in a predetermined datum plane; b. meansdetecting the position with respecT to said datum plane and the lastsense of movement of said force-applying means and generating outputsignals exclusively upon the occurrence of predetermined detectedpositions with respect to said datum plane and predetermined detectedsenses of movement of said force-applying means; c. a tension controlleroperatively responsive to said output signals to vary the speed ofoperation of one of said mechanisms relative to the other said mechanismexclusively during occurrence of said output signals to maintain saidforce-applying means and said material in contacting engagement at saiddatum plane.
 2. The system claimed in claim 1 in which said tensioncontroller is connected to vary the speed of operation of said materialfeed mechanism, said takeup mechanism being maintained at asubstantially constant speed.
 3. The system claimed in claim 1 whereinsaid force-applying means comprises a shaft, a tension roller supportedfor rotation on said shaft and contactingly engaging said material, saidshaft being supported by first and second rolamite assemblies formovement relative to said datum plane in accordance with movement ofsaid material, said shaft being connected to first rollers of saidassemblies.
 4. The system claimed in claim 3 including further a thirdrolamite assembly having a member interconnecting a first roller thereofto said first roller of said first rolamite assembly, said meansdetecting the positions with respect to said datum plane and senses ofmovement of said tension roller including a first switch member actuatedby said first rolamite assembly to one or another state by positioningof said tension roller on one or the other side of said datum plane anda second switch member actuated by said interconnecting member to on oranother state in accordance with the last sense of movement of saidtension roller.
 5. The system claimed in claim 4 wherein said meansdetecting the positions and senses of movement of said tension rollerfurther includes circuitry interconnecting a power supply and said firstand second switches for generation of said output signals, first outputsignals being provided exclusively when both said first and secondswitches are actuated to said one state or when both said first andsecond switches are actuated to said other state.
 6. The system claimedin claim 5 wherein said first switch comprises a proximity switchactuated by presence of the band of said rolamite within the switchfield of view, and said second switch is an attitude-sensitive switchaffixed to said interconnecting member.
 7. The system claimed in claim 1including a subsystem conforming the speed of operation of said feedmechanism to the speed of operation of said takeup mechanism comprising:a. a first signal generator providing an output signal indicative of thespeed of operation of said feed mechanism; b. a second signal generatorproviding an output signal indicative of the speed of operation of saidtakeup mechanism; and c. a speed controller operative alternatively tosaid tension controller upon demand to vary the speed of operation ofsaid feed mechanism, and responsive to differences between said outputsignals of said first and second signal generators.
 8. The systemclaimed in claim 1 wherein said position and sense detecting meansprovides a first or second output signal respectively upon the detectionof first position with respect to said datum plane and first directionallast sense of movement or second position with respect to said datumplane and second directional last sense of movement of saidforce-applying means, said tension controller increasing or decreasingthe speed of operation of said feed mechanism respectively in responseto said first or second output signals.
 9. The system claimed in claim 8wherein said tension controller includes means operatively responsive tosaid first or second output signal to respectively generate first orsecond successions of digital signals duriNg occurrence of said outputsignals, each signal in said first or second succession of signalsrespectively providing incremental increase or decrease in the speed ofoperation of said feed mechanism.
 10. The system claimed in claim 1wherein said position and sense of detecting means comprises a firstshaft, means supporting said first shaft for translation in a firstplane, said shaft supporting a tension roller in contacting engagementwith said transported material, a second rotatably supported shaftconnected to said first shaft and operated thereby in one or the otherrotational direction upon translation of said first shaft respectivelyin one or the other translational direction, a cam affixed to saidsecond shaft for rotation therewith and having first and second camsurfaces respectively indicative of the position of said first shaftabove or below a plane transverse to said plane of translation of saidfirst shaft, cam follower means continuously contacting said cam, asignal generator connected to said cam follower and providing first orsecond output signals in accordance with said positions of said firstshaft, a bidirectional slip clutch driven by said second shaft, anactuator connected to said slip clutch and second and third signalgenerators disposed on alternate sides of said actuator and respectivelyoperated by said actuator upon clockwise or counterclockwise rotation ofsaid second shaft and providing output signals respectively indicativeof first or second senses of translation of said first shaft.